Patent GB-852858-A (GB)
Title: Improvements in propeller-synchronising simulating systems
IPC: G09B9/18
Filed: 1959-01-30
Abstract: 852,858. Flight training apparatus. CURTISSWRIGHT CORPORATION. Jan. 30, 1959 [Feb. 13, 1958], No. 3468/59. Class 4. In flight training apparatus means is provided for synchro-phasing the propeller system of multi-engine aircraft. In the embodiment a simulated master engine that is regulated according to desired speed, controls three simulated slave engines, though a simulated master speed device may be used to control and synchronise all the engines. The system comprises a master speed control 1, a plurality of motors 2, 3 and 4 representing slave engines to be synchronized and circuting 5 connecting the master control and the individual motors, the master control and each motor being mechanically connected to individual enginepropeller sound systems shown more fully at 6 but indicated diagrammatically at other positions by tone-wheels 7, 8 and 9. Control 1 is supplied from a computing r.p.m. servo system 10 of known type with a signal representing the master r.p.m., wherein the servo amplifier 11 controls through a M-G unit 12 the slider 13<SP>1</SP> of a potentiometer 13 energised by an A.C. voltage Eac, the derived signal being fed to the master r.p.m. amplifier 14, the output of which energises a M-G unit 15 to drive through mechanical connection 16 the primary winding 17 of a synchronous transformer 18 and also the tone generating wheel 19 of sound system 6. Wheel 19 is formed with apertures 19a and 19b for representing respectively propeller " slap " and engine exhaust explosions, the apertures being aligned with a light beam 20 projected at 21 on to a photo-electric tube 22, the signals from which are amplified at 23 to energise a loudspeaker 24. The primary winding 17 is energised by an A.C. voltage Eac through slip ring 25 and earthed through slip ring 26. Slip ring connections in other parts of the circuit are indicated by breaks SR. The secondary winding 27 of transformer 18 comprises a three phase winding from which speed-controlling signals are transmitted to corresponding parallel-connected three-phase windings 28, 29 and 30 of the respective synchronous receivers 31, 32 and 33. The secondary windings 34, 35 and 36 of the synchronous receivers are connected through proportioning input resistors to the input sides of respective servomotor amplifiers 37, 38 and 39, the outputs of which energise motors 2, 3 and 4 respectively to drive tone wheels 7, 8 and 9. Simulation of synchro phasing control is accomplished by the application of biassing signals to the amplifiers 37, 38 and 39 from potentiometers 43, 47 and 48 respectively which are grounded at mid-point and energised from a reference voltage Eac. The wipers of the potentiometers are adjusted by dials 44, 49 and 50 operated by the student so that a signal of appropriate sense may be superimposed on the speed synchronizing signals whereby the relative phase positions of the tone wheels can be individually shifted relative to each other and to the master engine so that the combined volume of simulated engine and propeller noise can be reduced to its minimum. In a further embodiment (not shown) phasing control is achieved by inserting additional synchronous transformers in each of the branch circiuts between the master transformer 18 and the respective synchronous receivers 31, 32 and 33. Specification 766,184 is referred to.